1. Field of the Invention
This invention relates to dimensionally stabilized lignocellulosic material and a dimensional stabilization process.
2. Description of the Prior Art
It is well known that lignocellulosic materials made up predominantly or entirely of cellulosic fibers, hereinafter described in terms of wood, are sensitive to the effects of water, and expand and contract with variations in humidity in the atmosphere. Such changes in the dimensions of wood are particularly undesirable when the wood is used as a structural material. In a very humid atmosphere the wood may swell until a saturation moisture content of about 30% is obtained, this moisture content being known as the "fiber-saturation point". Below the fiber-saturation point, the water is believed to enter the fine capillary structure of the cell walls of the wood and affect the dimensions of the wood. Above the fiber-saturation point, additional water is believed to enter the cell cavities or coarse capillary structure and usually does not affect the dimensions of the wood under normal conditions.
Techniques for the stabilization of wood are known. Such techniques include the use of coatings, deposition of bulking agents in the cell walls of the wood, decreased hygroscopicity plus bulking and the use of chemical cross-linking agents.
U.S. Pat. No. 3,077,417 describes the use of acrylic monomers in the dimensional stabilization of wood, while U.S. Pat. No. 3,077,419 describes an alternate technique using vinyl substituted aryl monomers. U.S. Pat. No. 3,077,418 describes the use of a styrene mixture to dimensionally stabilize wood. Wood treated with methyl methacrylate and/or styrene is also known and may be used as a flooring, in particular in the form of parquet flooring.
In a typical process for the dimensional stabilization of wood with ethylenically unsaturated monomers, the wood is impregnated with the ethylenically unsaturated monomers and subsequently the monomers are polymerized, thereby giving wood of improved dimensional stability.
Dimensionally stabilized wood is capable of being used as window and/or door frames in buildings as well as in the form of flooring. However, the known techniques for the dimensional stabilization of wood generally are capable of improvement, especially with respect to the degree of dimensional stabilization obtained.